The invention disclosed herein pertains to a laser power meter wherein incident laser radiation is converted to thermal energy which is transferred to a flowing fluid, the temperature rise and the flow rate of the fluid defining the power output of the laser.
Laser power meters wherein laser energy is transferred to a flowing fluid are disclosed in U.S. Pat. No. 3,464,267 to Ehrlich et al and U.S. Pat. No. 2,560,536 to Althouse. The laser power meter disclosed in U.S. Pat. No. 3,464,267 to Ehrlich et al includes a housing having a conical cavity. The laser radiation is directed onto the inner surface of the conical cavity where it is converted into thermal energy. A plurality of cooling fins are provided about the outer surface of the conical cavity. These fins project into a coolant passage about the outer surface of the conical cavity which is defined by a conical member which is coaxial with, and spaced from, the conical cavity. Water flowing through the coolant passage absorbs the thermal energy generated by the laser radiation impinging upon the inner surface of the conical cavity, resulting in a temperature increase of the water. The response rate of the apparatus is directly proportional to the flow rate of the water. The temperature increase of the water is sensed by temperature sensors which are incorporated in a bridge circuit where the amount of unbalance of the bridge is proportional to the temperature increase and hence to the average power in the laser beam.
U.S. Pat. No. 2,560,536 to Althouse discloses a device for measuring the power of electromagnetic radiation conducted through a wave guide. The Althouse device includes a wave guide load termination coupled to the wave guide. The load termination includes a horizontal top surface, vertical side walls, a vertical end plate, and a bottom wall. The bottom wall includes a horizontal portion and an upwardly inclined portion extending to the end plate. A thin film of water flows over the upwardly inclined portion of the bottom wall. This water is supplied through an inlet conduit arranged near the intersection of the horizontal and the upwardly inclined portions of the bottom wall, and the thin film of water flows out through an outlet conduit arranged at the intersection of the upwardly inclined portion of the bottom wall and the end plate. A shield is arranged within the load termination, which shield is parallel to, and spaced from, the upwardly inclined portion. A valve in the inlet conduit is adjustable to establish a constant fluid flow, of film thickness, over the entire surface of the inclined portion of the bottom wall. Temperature sensors are provided at the inlet and outlet conduits, the temperature differential measured by these sensors being directly proportional to the power of the electromagnetic energy directed into the wave guide load termination.
Other laser power meters are disclosed in the following patents: U.S. Pat. No. 3,596,514 to Mefferd et al; U.S. Pat. No. 3,783,685 to Zeiders, Jr. et al; U.S. Pat. No. 3,918,303 to Zakhidov et al; U.S. Pat. No. 4,037,470 to Mock et al; and British Pat. No. 1,271,239 to Paine.
While the prior art does disclose various types of laser power meters, wherein laser energy is transferred to a cooling fluid, the prior art does not disclose a laser power meter like that of the present invention.